This invention arose from a need to effectively automate the lining of cartons by insertion of an open plastic bag. Such lined carton assemblies are widely used for packing of fresh meat and other food products.
Examples of prior patents disclosing equipment for inserting and cuffing plastic bags in a carton assembly are shown in U.S. Pat. Nos. 4,142,453 to Gidewall et al., 4,522,012 to Nelson and 4,729,209 to Owensby et al.
The Gidewall et al. patent discloses equipment in which individual plastic bags are manually placed about a mandrel prior to insertion. Cuffing is accomplished by pivoting folder assemblies 120, illustrated as opposed plates 128 that are each wider than the inserting mandrel. A diagrammatic illustration of these plates is shown in FIG. 7 of the patent drawings, where the folder plates are indicated by numeral 30, the cuffed opening of the bag is illustrated at 31, and the receiving carton is illustrated at 32.
The Nelson patent removes individual bags from a supply roll as the inserting mandrel moves downwardly toward the receiving carton. Four cuffing fingers 125 spread the open mouth of each bag for cuffing purposes. The cuffing fingers extend at about a 45.degree. angle relative to each corner of the receiving carton. This type of cuffing arrangement is diagrammatically illustrated in FIG. 6, where the fingers are designated by the numeral 33, the cuffed portion of the bag is designated at 34 and the carton is indicated at 35.
The Owensby patent discloses use of downwardly depending fingers which act as spreader means and means to hold the upper portion of the bag, which is supplied from a stack. The fingers are carried on the inserting mandrel and the spreading function is provided by an activating mechanism 17. The linkage 17 moves the spreader fingers outwardly to spread out the mouth of the bag and to form a cuff about the outer perimeter of the box. No details are provided with respect to the fingers, which is part of an outer mandrel shown at 10 in the referenced patent disclosure. It appears from the patent description that the spread fingers assume the positions shown in FIG. 6 of the drawings submitted with this disclosure.
Similar cuffing mechanisms have been described in prior patents pertaining to related equipment for cuffing plastic bags in a nested configuration. Four cuffing bars located at four corners of a support plate are described in U.S. Pat. No. 3,606,821 to Tsien. Four cuffing fingers are also illustrated and described in U.S. Pat. No. 3,796,140 to Adams et al., and are diagrammatically shown as items 66-69 in FIG. 7 of the drawings for that patent.
So far as can be determined, all of the spreading and cuffing mechanisms that have preceded the present invention have required that the bag be spread diagonally outward beyond each corner of the receiving carton. Since the spreading fingers or bars have a thickness that must be accommodated during the cuffing operation, this requires that the dimensions of the bag being inserted into a carton be somewhat greater than the interior carton dimensions. It is not practical to substantially stretch the plastic material of the bag for the cuffing procedures. This would either deform or tear the mouth of the bag or would result in frictional forces being developed against the spreading elements to a degree that would impede their subsequent removal from the cuffed opening.
Another difficulty with previously-known cuffing mechanisms is the inability to grip or hold the bag during removal of the mandrel and spreading elements. Any inward pressure exerted on the cuffed portions of the bags between the corner spreading elements will greatly increase the frictional engagement between the cuffed bag and spreading elements.
The present improvement permits substantial reductions to be made in the size of inserted bags that are cuffed over a receiving carton. It also facilitates use of selective clamping forces to engage the exterior of the cuffed bag opening and thereby assist in the removal of spreading fingers from within the bag without pulling the bag with them.